Robust C-C bonded porous networks with chemically designed functionalities for improved CO2 capture from flue gas

Article abstract of DOI:10.3762/bjoc.12.220

Effective carbon dioxide (CO₂) capture requires solid, porous sorbents with chemically and thermally stable frameworks. Herein, we report two new carbon-carbon bonded porous networks that were synthesized through metal-free Knoevenagel nitrile-aldol condensation, namely the covalent organic polymer, COP-156 and 157. COP-156, due to high specific surface area (650 m²/g) and easily interchangeable nitrile groups, was modified post-synthetically into free amine- or amidoxime-containing networks. The modified COP-156-amine showed fast and increased CO₂ uptake under simulated moist flue gas conditions compared to the starting network and usual industrial CO₂ solvents, reaching up to 7.8 wt % uptake at 40°C.

Full text of DOI:10.3762/bjoc.12.220

Robust C–C bonded porous networks with chemically
designed functionalities for improved CO2 capture
from flue gas
Damien Thirion1, Joo S. Lee1, Ercan Özdemir1 and Cafer T. Yavuz*1,2,§
Letter
Open Access
Address:
Graduate School of Energy, Environment, Water, Sustainability
Beilstein J. Org. Chem. 2016, 12, 2274–2279.
1
doi:10.3762/bjoc.12.220
(EEWS), Korea Advanced Institute of Science and Technology
(
KAIST), Guseong Dong, Yuseong Gu, Daejeon 305–701, Korea and
Received: 05 August 2016
Accepted: 14 October 2016
Published: 28 October 2016
2
Department of Chemistry, Korea Advanced Institute of Science and
Technology (KAIST), Guseong Dong, Yuseong Gu, Daejeon
05–701, Korea
3
This article is part of the Thematic Series "Organic porous materials".
Guest Editor: S. Bräse
Email:
Cafer T. Yavuz* - yavuz@kaist.ac.kr
*
Corresponding author
© 2016 Thirion et al.; licensee Beilstein-Institut.
License and terms: see end of document.
§
www.porouspolymers.com, Tel: +82-42-350-1718
Keywords:
C–C bond; CO2 capture; microporous materials; porous polymers;
postmodification
Abstract
Effective carbon dioxide (CO2) capture requires solid, porous sorbents with chemically and thermally stable frameworks. Herein,
we report two new carbon–carbon bonded porous networks that were synthesized through metal-free Knoevenagel nitrile–aldol
condensation, namely the covalent organic polymer, COP-156 and 157. COP-156, due to high specific surface area (650 m2/g) and
easily interchangeable nitrile groups, was modified post-synthetically into free amine- or amidoxime-containing networks. The
modified COP-156-amine showed fast and increased CO2 uptake under simulated moist flue gas conditions compared to the
starting network and usual industrial CO2 solvents, reaching up to 7.8 wt % uptake at 40 °C.
Findings
Porous polymers are network polymers that are made from criteria like high porosity, chemical and thermal stability while
multivalent monomers and form permanent pores through the also possessing application-specific functionalities [1,2].
net formation [1]. They differ slightly from cross-linked poly- Designing and synthesizing structures that respect all these
mers with more certainty in the location of branching and the criteria is a challenging task. Chemical and thermal stability can
type and quantity of functionalities. Also, the rigidity of the be achieved best by having robust C–C bonded architecture like
monomers is essential since the porosity, a desired feature, is in porous polymer networks (PPNs) [3], porous aromatic frame-
best achieved by structurally interlocked motifs. In industrial works (PAFs) [4] or conjugated microporous polymers (CMPs)
applications, porous polymers have to meet several important [5]. Most of these networks have the advantage of high
2274

Beilstein J. Org. Chem. 2016, 12, 2274–2279.
porosity, but they are all made through precious metal-cata- explored in other types of porous polymers, except our earlier
lyzed reactions, which elevates the synthesis cost and limits work [18].
their mass production. Another type of C–C bonded porous
networks are hypercrosslinked polymers (HCPs) [6]. HCPs are Herein we report the synthesis of two new cyanovinylene-
mainly synthesized through Friedel–Crafts alkylation using iron bridged covalent organic polymers, indexed as COP-156 and
chloride and thus, are not relying on precious metals. Unfortu- COP-157, through Knoevenagel nitrile–aldol condensation.
nately, Friedel–Crafts reactions are not very tolerant to func- COP-156 showed a high surface area (650 m2/g) with a hierar-
tional groups like nitriles or amines [7]. On the other hand, chical porosity, allowing synthetic post-modifications. The
structures incorporating heteroatoms, such as nitrogen in imine, nitrile functional groups were first reduced to amine groups
Tröger’s base or azo linked networks [8-11], have led to materi- (COP-156-amine) and then through reaction with hydroxyl-
als with remarkable gas uptake properties. Compared to C–C amine converted into amidoxime groups (COP-156-
bonded networks, C–O or C–N linked structures are less ther- amidoxime). The COP-156-amine proved increased affinity
mally stable or chemically resistant. Furthermore, the chemical towards CO2 with stronger binding energy, especially under
reactions involved in the formation of these structures do not moist conditions, reaching up to 7.8 wt % at 40 °C, a 2.1 wt %
allow obtaining free nitrile or amine functionalities. The most increase when compared to the original COP-156.
used strategy to install available functional groups on porous
materials is through post-modification, which often requires Despite the promise, cyanovinylene bridged porous networks
several steps and harsh conditions, and yields low porosity are not studied extensively and our previously reported COP-
[
12,13].
100 structure [18] suffered from low porosity. In order to obtain
a cyanovinylene-bridged porous network with tangible surface
The Knoevenagel condensation of benzyl nitriles and alde- area, different core and linker combinations were tested leading
hydes produces C–C bonded products with labile nitrile func- to the synthesis of COP-156 and COP-157 (Scheme 1).
tionalities. In fact, nitrile groups have been shown in porous Tetraphenylmethane cores are well-known tetrahedral building
polymers (particularly in polymers of intrinsic microporosity blocks that are commonly employed to form highly porous ma-
(
PIMs)) to be good precursors to several functionalities like terials [4,19]. A trivalent 1,3,5-phenylenetriacetonitrile linker
carboxylic acids, tetrazoles, amines or amidoximes [14-17]. To led to COP-156 whereas a divalent 1,4-phenylenediacetonitrile
the best of our knowledge the nitrile functionality has not been formed COP-157 (Scheme 1). Despite having the same tetra-
Scheme 1: Synthesis route for COP-156 and COP-157, and the post-modification of COP-156.
2275

Beilstein J. Org. Chem. 2016, 12, 2274–2279.
hedral core, COP-156 showed a much higher surface area
650 m2/g) than COP-157 (146 m2/g). One possible reason is
(
the framework interpenetration, where neighboring branches of
a network polymer intertwine through the adjacent open pore.
For these reasons, we studied COP-156 for post-modification.
COP-156 possesses labile nitrile functionalities, which can
easily be transformed into amines or amidoximes. Amines are
especially attractive for gas uptake [20] and amidoximes are
shown effective in uranium capture [21]. COP-156 has been
post-modified through two different routes, either by reduction
to the corresponding amine or reaction with hydroxylamine into
an amidoxime. For the reduction, three reagents (LiAlH4,
BH3–THF and BH3–Me2S) were screened. All reductions were
chemically successful, but the textural properties of the modi-
fied networks were noticeably different. BH3–Me2S gave the
highest surface area and therefore CO2 uptake studies were
based on this reduction method (see Supporting Information
File 1, Table S1 for the properties of other obtained reduced
networks). All networks were studied by FTIR, elemental anal-
ysis, TGA, and gas sorption experiments.
Figure 1: FTIR spectra of COP-156 (black), COP-156-amine (blue)
and COP-156-amidoxime (red). The dotted lines highlight the charac-
teristic stretching for the nitrile functionality (2215 cm−1), which loses
intensity by the post-modification reactions.
Brunauer–Emmett–Teller (BET) theory. COP-156 shows
type II N2 sorption isotherms and a slight hysteresis, owing to
The FTIR spectra of COP-156 shows the characteristic nitrile the existence of micro, meso and macropores, with a surface
stretch at 2215 cm−1 and several bands for the carbon–carbon area of 650 m2/g and a pore volume of 0.82 cm3/g at
double bonds (C=C) of both aromatic and alkene between 1600 P/P0 = 0.99 (Figure 2). The pore size distribution is broad with
and 1350 cm−1 (Figure 1). The presence of a peak at 1698 cm−1 several important pore sizes (2.2, 3.0, 5.0, 7.0 nm). Larger pores
can be attributed to carbonyl units from unreacted aldehydes. are required for post-modification, as the reagents may not be
This is further confirmed in elemental analysis showing the able to penetrate to the small micropores. CO2 sorption iso-
presence of 4–5 % oxygen (Supporting Information File 1, Ta- therms reflect the physisorptive nature of COP-156 with almost
ble S2). The condensation reaction is very fast and the formed no hysteresis and an isosteric heat of adsorption (Qst) of
network precipitates in a matter of minutes, leading to unre- 28.1 kJ mol−1 (Table 1, Figure 2 and Supporting Information
acted aldehyde edges on the surface of the grains, explaining File 1, Figure S3). COP-157 gave a similar isotherm but with
the leftover carbonyl units. COP-157 shows similar results due lesser surface area (Supporting Information File 1, Figures S4
to the chemical similarity of the structures and the reaction and S5). This could be explained by a higher interpenetration
conditions (Supporting Information File 1, Figure S1 and Table probability of the network structure than in COP-156, as the
S2).
linker used for COP-157 is linear [22,23].
After post-modification, the nitrile stretching becomes very After post-modification, the surface area diminishes, which is a
weak in both COP-156-amine and COP-156-amidoxime, common observation [13,24]. Yet, the pore volume of COP-
confirming the chemical modification of the nitrile units 156-amine increases to 0.99 cm3/g at P/P0 = 0.99, due to newly
(
Figure 1). A broad region around 3400 cm−1 can be attributed created pores from the reduction reaction (Figure 2). COP-156-
to the NH stretching of the formed amine groups and the two amidoxime has decreased both surface area (67 m2/g) and pore
peaks at 2931 and 2866 cm−1 belong to sp3 CH stretching of the volume (0.41 cm3/g at P/P0 = 0.99), as the functional group is
formed methylene unit in COP-156-amine. For COP-156- larger than amine or nitrile. It should be noted that elemental
amidoxime the 3400 cm−1 region is even broader, due to the analysis does not reach 100% with the measured elements (C,
combination of both NH and OH stretching. The strong peak at H, N, O), indicating the presence of trapped reagents in the
1
664 cm−1 can be attributed to the imine C=N bond of the pores. These could not be removed with extensive washing and
amidoxime structure.
therefore contribute to the porosity loss (Supporting Informa-
tion File 1, Table S2). Nevertheless, CO2 sorption isotherms of
The textural properties were measured through nitrogen sorp- COP-156-amine show a slight hysteresis, indicating that the
tion isotherms at 77 K and calculated based on the network is not purely physisorptive anymore. At 0.15 bar (the
2276

Beilstein J. Org. Chem. 2016, 12, 2274–2279.
Figure 2: Gas adsorption (filled dots)-desorption (empty dots) isotherms and pore size distribution of COP-156 (black), COP-156-amine (blue) and
COP-156-amidoxime (red).
Table 1: BET surface area, CO2 sorption properties at 273 K, 298 K and heat of adsorption values of all networks.
Structure
BET surface area (m2/g)
CO2 at 273 K
mmol/g) 0.15/1 bar
CO2 at 298 K
(mmol/g) 0.15/1 bar
Qst (kJ/mol)a
(
COP-156
650
146
263
67
0.84/2.31
0.45/1.18
0.94/2.00
0.47/1.10
0.38/1.40
0.22/0.71
0.34/1.09
0.20/0.58
28.1
29.5
49.9
38.6
COP-157
COP-156-amine
COP-156-amidoxime
aZero point coverage Qst calculated from 273 K and 298 K.
relevant pressure of CO2 in flue gas emission) and 273 K, the Dry CO2 uptake is not always meaningful, especially with
uptake is slightly higher than the starting COP-156. The amine functionalities, as flue gas from power plants contains
chemisorptive behavior and stronger binding affinity is re- moisture [26]. When binding to CO2, amines go through either
flected in the higher Qst value of 49.9 kJ mol−1. The moderate carbamate or carbamic acid formation. Carbamates form with
binding energy is optimal for CO2 capture, as too strong the contribution of two amines and carbamic acid needs one
binding requires high regeneration energy and raises the overall amine and a water molecule. The presence of moisture, there-
cost of the carbon capture operations [12,25].
fore, favors the formation of carbamic acids and leads to higher
2277

Beilstein J. Org. Chem. 2016, 12, 2274–2279.
uptake capacity per sorbent mass. We performed moist CO2 Acknowledgements
uptake experiments in order to mimic an actual power plant flue This work was supported by the National Research Foundation
gas on COP-156 and COP-156-amine (see Supporting Informa- of Korea (NRF) grant funded by the Korea government (MSIP)
tion File 1 for the experimental details).
(No. NRF-2016R1A2B4011027).
As expected, COP-156-amine shows faster and higher uptake References
than COP-156 (Figure 3). For the COP-156-amine 80% of the 1. Wu, D.; Xu, F.; Sun, B.; Fu, R.; He, H.; Matyjaszewski, K. Chem. Rev.
2
012, 112, 3959. doi:10.1021/cr200440z
total CO2 uptake is reached in 21 minutes, while COP-156
requires around 30 minutes to reach the same percentage. COP-
2
.
.
Slater, A. G.; Cooper, A. I. Science 2015, 348, 6238.
doi:10.1126/science.aaa8075
1
56-amine yields a total uptake of 7.8 wt %, which is 2.1 wt %
3
Lu, W.; Yuan, D.; Zhao, D.; Schilling, C. I.; Plietzsch, O.; Muller, T.;
Bräse, S.; Guenther, J.; Blümel, J.; Krishna, R.; Li, Z.; Zhou, H.-C.
Chem. Mater. 2010, 22, 5964. doi:10.1021/cm1021068
Ben, T.; Ren, H.; Ma, S.; Cao, D.; Lan, J.; Jing, X.; Wang, W.; Xu, J.;
Deng, F.; Simmons, J. M.; Qiu, S.; Zhu, G. Angew. Chem., Int. Ed.
more than COP-156. These CO2 capacities are considerably
higher than the industrial standard, monoethanolamine (MEA)
4.
(
usually 2.1–5.5 wt %) [27,28].
2009, 48, 9457. doi:10.1002/anie.200904637
5
.
.
Cooper, A. I. Adv. Mater. 2009, 21, 1291.
doi:10.1002/adma.200801971
6
Martin, C. F.; Stöckel, E.; Clowes, R.; Adams, D. J.; Cooper, A. I.;
Pis, J. J.; Rubiera, F.; Pevida, C. J. Mater. Chem. 2011, 21, 5475.
doi:10.1039/c0jm03534c
7
.
.
.
Dawson, R.; Ratvijitvech, T.; Corker, M.; Laybourn, A.; Khimyak, Y. Z.;
Cooper, A. I.; Adams, D. J. Polym. Chem. 2012, 3, 2034.
doi:10.1039/c2py20136d
8
Patel, H. A.; Je, S. H.; Park, J.; Chen, D. P.; Jung, Y.; Yavuz, C. T.;
Coskun, A. Nat. Commun. 2013, 4, No. 1357.
doi:10.1038/ncomms2359
9
1
1
1
Byun, J.; Je, S.-H.; Patel, H. A.; Coskun, A.; Yavuz, C. T.
J. Mater. Chem. A 2014, 2, 12507. doi:10.1039/C4TA00698D
0.Côté, A. P.; Benin, A. I.; Ockwig, N. W.; O'Keeffe, M.; Matzger, A. J.;
Yaghi, O. M. Science 2005, 310, 1166. doi:10.1126/science.1120411
1.Schwab, M. G.; Fassbender, B.; Spiess, H. W.; Thomas, A.; Feng, X.;
Müllen, K. J. Am. Chem. Soc. 2009, 131, 7216. doi:10.1021/ja902116f
2.Islamoglu, T.; Kim, T.; Kahveci, Z.; El-Kadri, O. M.; El-Kaderi, H. M.
J. Phys. Chem. C 2016, 120, 2592. doi:10.1021/acs.jpcc.5b12247
Figure 3: CO2 uptake under moist conditions at 40 °C of COP-156
(black) and COP-156-amine (blue).
13.Lu, W.; Sculley, J. P.; Yuan, D.; Krishna, R.; Wei, Z.; Zhou, H.-C.
Angew. Chem., Int. Ed. 2012, 51, 7480. doi:10.1002/anie.201202176
1
4.Patel, H. A.; Yavuz, C. T. Chem. Commun. 2012, 48, 9989.
doi:10.1039/c2cc35392j
In summary, we have shown that highly porous cyanovinylene
networks could be obtained through Knoevenagel condensation
of benzylic nitriles and aldehydes by choosing appropriate
building blocks. The resulting nitrile functionalities in COP-156
could be easily modified into free amine or amidoxime groups.
The amine functionalities in COP-156-amine allowed for higher
CO2 binding strength and therefore led to fast and improved
CO2 uptake in moist conditions.
1
5.Mason, C. R.; Maynard-Atem, L.; Heard, K. W. J.; Satilmis, B.;
Budd, P. M.; Friess, K.; Lanč, M.; Bernardo, P.; Clarizia, G.;
Jansen, J. C. Macromolecules 2014, 47, 1021.
doi:10.1021/ma401869p
1
6.Du, N.; Park, H. B.; Robertson, G. P.; Dal-Cin, M. M.; Visser, T.;
Scoles, L.; Guiver, M. D. Nat. Mater. 2011, 10, 372.
doi:10.1038/nmat2989
1
1
1
2
7.Weber, J.; Du, N.; Guiver, M. D. Macromolecules 2011, 44, 1763.
doi:10.1021/ma101447h
8.Özdemir, E.; Thirion, D.; Yavuz, C. T. RSC Adv. 2015, 5, 69010.
doi:10.1039/C5RA10697D
Supporting Information
9.Yuan, D.; Lu, W.; Zhao, D.; Zhou, H.-C. Adv. Mater. 2011, 23, 3723.
doi:10.1002/adma.201101759
Supporting Information File 1
0.Zulfiqar, S.; Karadas, F.; Park, J.; Deniz, E.; Stucky, G. D.; Jung, Y.;
Atilhan, M.; Yavuz, C. T. Energy Environ. Sci. 2011, 4, 4528.
doi:10.1039/c1ee02264d
Materials and methods, synthesis, FTIR spectra and gas
sorption isotherms of COP-157, heat of adsorption graph,
elemental analysis and TGA of all structures.
21.Sihn, Y. H.; Byun, J.; Patel, H. A.; Lee, W.; Yavuz, C. T. RSC Adv.
[http://www.beilstein-journals.org/bjoc/content/
2016, 6, 45968. doi:10.1039/C6RA06807C
supplementary/1860-5397-12-220-S1.pdf]
22.Kitagawa, S.; Kitaura, R.; Noro, S.-i. Angew. Chem., Int. Ed. 2004, 43,
334. doi:10.1002/anie.200300610
2
2278

Beilstein J. Org. Chem. 2016, 12, 2274–2279.
23.Batten, S. R.; Robson, R. Angew. Chem., Int. Ed. 1998, 37, 1460.
doi:10.1002/(SICI)1521-3773(19980619)37:11<1460::AID-ANIE1460>3
.0.CO;2-Z
Angew. Chem. 1998, 110, 1558.
doi:10.1002/(SICI)1521-3757(19980605)110:11<1558::AID-ANGE1558
>
3.0.CO;2-7
4.Islamoğlu, T.; Rabbani, M. G.; El-Kaderi, H. M. J. Mater. Chem. A
013, 1, 10259. doi:10.1039/c3ta12305g
2
2
2
5.Thirion, D.; Rozyyev, V.; Park, J.; Byun, J.; Jung, Y.; Atilhan, M.;
Yavuz, C. T. Phys. Chem. Chem. Phys. 2016, 18, 14177.
doi:10.1039/C6CP01382A
2
6.Fracaroli, A. M.; Furukawa, H.; Suzuki, M.; Dodd, M.; Okajima, S.;
Gándara, F.; Reimer, J. A.; Yaghi, O. M. J. Am. Chem. Soc. 2014, 136,
8863. doi:10.1021/ja503296c
2
7.Boot-Handford, M. E.; Abanades, J. C.; Anthony, E. J.; Blunt, M. J.;
Brandani, S.; Mac Dowell, N.; Fernández, J. R.; Ferrari, M.-C.;
Gross, R.; Hallett, J. P.; Haszeldine, R. S.; Heptonstall, P.; Lyngfelt, A.;
Makuch, Z.; Mangano, E.; Porter, R. T. J.; Pourkashanian, M.;
Rochelle, G. T.; Shah, N.; Yao, J. G.; Fennell, P. S.
Energy Environ. Sci. 2014, 7, 130. doi:10.1039/C3EE42350F
8.Porcheron, F.; Gibert, A.; Mougin, P.; Wender, A.
2
Environ. Sci. Technol. 2011, 45, 2486. doi:10.1021/es103453f
License and Terms
This is an Open Access article under the terms of the
Creative Commons Attribution License
(http://creativecommons.org/licenses/by/4.0), which
permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
The license is subject to the Beilstein Journal of Organic
Chemistry terms and conditions:
(http://www.beilstein-journals.org/bjoc)
The definitive version of this article is the electronic one
which can be found at:
doi:10.3762/bjoc.12.220
2279